The invention relates to an apparatus for colour electrophotography, and more particularly to such apparatus which performs the steps of charging, exposure and transfer of an electrostatic latent image formed while maintaining both an original and a copy sheet stationary.
In colour electrophotography, a colour image is obtained by successively forming a number of visual images of different colours corresponding to different filters used in the process of colour separation of the image of the original, which colour image is formed on a copy sheet in a superimposed manner. As a specific transfer means for such colour electrophotography, a photosensitive member having a layer of photoconductive material may be used to form visual images by repeating the steps of charging, exposure and developing. Alternatively, a visual image may be transferred onto another sheet, but this involves the possibility that the response of the layer of photoconductive material may be impeded, since an electrostatic latent image must be formed during these cycles by the steps of charging and exposing the photosensitive member which carries a visual image thereon. The compensation of this required the provision of various special means. In addition, the transfer of a visual image cannot be expected to be perfect since it is a transfer of a tangible material.
On the other hand, a drum is customarily used as a photosensitive member in the art of colour electrophotography and is rotated at a determined position during the steps of charging, exposure and developing. In this instance, the exposure optical system must be capable of moving back and forth in correspondence to the rotation of the photosensitive member, which resulted in a complicate construction and control of the apparatus as well as a reduction in the copying efficiency.